Major goals for enhancing the performance of charge storage parts such as thin-film capacitors in the prior art have included improving the capacity density and reducing the leakage current density of dielectric thin-films sandwiched between electrodes.
For formation of a dielectric thin-film by a wet process, first a metal oxide thin-film starting solution for the dielectric layer is applied on a surface of a substrate. The applied starting solution is then fired to form a metal oxide thin-film. Firing atmospheres used in the prior art are oxygen atmospheres to prevent oxygen deficiency of the dielectric material (for example, see Patent document 1). When strontium titanate thin-films are formed as metal oxide thin-films, on the other hand, it has been possible to reduce the leakage current density of the strontium titanate thin-films by limiting the atomic ratio of strontium atoms to titanium atoms to no greater than 1 (for example, see Non-patent document 1).
However, Non-patent document 1 also reports lower capacity density with strontium titanate thin-films when the atomic ratio strontium atoms to titanium atoms is below 1.
[Patent document 1] Japanese Patent Application Laid-Open HEI No. 9-78249
[Non-patent document 1] R&D Review of Toyota CRDL, Vol. 32, No. 3 (September 1997) pp 61-70.